1. Field of the Invention
This invention relates to open cycle power generation systems utilizing ocean water temperature differences and more particularly to means for controlling electrical output of the system.
2. Description of the Prior Art
Alternative power generation sources have recently been sought to augment present generation capacity. Solar energy has been found to have some advantages over more conventional power generation means. A serious disadvantage of solar energy has, heretofore, been the relatively high cost of the solar collectors required to gather the solar energy. A concept has recently evolved which utilizes the ocean surface water as the solar collector. This concept involves flashing relatively warm, surface ocean water into steam and expanding that steam through a turbine to a condenser where relatively cold, subsurface ocean water is utilized to condense the expanded steam and maintain a relatively low pressure within the condenser. Due to the small pressure range (less than 15 pounds per square inch), the specific volume of motive steam used in the power cycle makes the use of conventional turnbine inlet control valves and stop valves impractical due to the extremely large size required and the fact that normal flow losses passing through such valves may approach the cycle's total pressure drop.
An ocean thermal energy conversion configuration was illustrated in U.S. Pat. No. 4,087,975 which issued May 9, 1978. Such patent showed a general outline of the vessel which houses an ocean thermal energy conversion system, but suggested no means for controlling the generator output from such system.
U.S. Pat. No. 3,750,395, which issued Aug. 7, 1973, to Tapper et al and is assigned to the assignee of the present invention, illustrates a power generation system which includes stop valves disposed upstream from the turbine and vacuum breaking valves connected to the condenser. As previously stated, stop valves such as those illustrated in the aforementioned patent are impractical for use on the present invention. Similar schemes which utilize stop valves between the motive steam source and turbine in combination with vacuum breaking valves for conventional power generation systems are illustrated in U.S. Pat. Nos. 2,409,024 and 879,121 which respectively issued Oct. 8, 1946 and Feb. 11, 1908. An additional disadvantage of the prior art vacuum breaking schemes as applied to low pressure, open cycles is the atmospheric air venting being directed to the condenser. Disposition of such air inlet provides relatively slow pressure response since low pressure, open cycle condensers are frequently large vessels requiring a not insubstantial time for filling with air.